1. Field of the Invention:
The present invention relates to photo- and electron-resists to be used in various microfabrications for the manufacture of semiconductor elements, integrated circuits and the like and a method of forming patterns with such resists.
2. Description of the Prior Art:
With the advance of microminiaturization and high-density integration of semiconductor elements, integrated circuits and the like, high performance resists for microfablication are demanded and many studies and developments are actively being made. However, resist materials including presently used photoresists are almost composed of organic polymer substances and there is not attempted a development of practical resist materials composed of inorganic substances other than the proposal of utilizing radiation sensitivity of chalcogenide materials as described below.
In general, the resist materials are required to have such fundamental functions that the solubility in a solvent is changed by irradiation of light, electron beam or the like and that they serve as a protective coating during the etching of the material to be worked. For this purpose, there are used two embodiments of resists composed of chalcogenide materials as proposed in U.S. Pat. No. 3,637,377 and No. 3,762,325. Firstly, a laminated thin film of an inorganic substance (mainly, chalogenide) and a metal is used as a radiation sensitive material, and secondarily, chalcogenide material is used alone. In any case, areas exposed to radiation are removed by etching or peeling off. That is, the photographic sensitivity is so-called positive. Further, the chalcogenide materials used contain arsenic as a main ingredient, a typical example of which is arsenic trisulfide (As.sub.2 S.sub.3).
These prior arts have the following drawbacks. That is, in the first embodiment, the chalcogenide material contains arsenic as the main ingredient and the exposed area is removed by etching, so that a high resolution cannot be obtained owing to the poor etched state. Further, the sensitivity and contrast as the radiation sensitive material are low. Moreover, the chalcogenide material is easily soluble in an alkaline solution, so that it cannot be applied to the processing with an alkali as an etchant. Particularly, since arsenic is a typical donor impurity against silicon, there is a contamination problem in the application for the manufacture of silicon semiconductor elements. When the inorganic substance layer and the metal layer are formed by vacuum evaporation as described in U.S. Pat. No. 3,637,377, undesirable reaction is caused between the inorganic substance and the metal by a light emitted from the evaporating sources during the evaporation.
In the second embodiment, there is a serious drawback that the difference of solubility between the exposed area and the non-exposed area is only by about two times. Further, there are such drawbacks that the etched state is poor and the sensitivity and contrast are low.